The auditory cortex is activated by silent, but sound-associated, visual stimuli reports an imaging study published online this week in Nature Neuroscience. The study shows that not only is the auditory cortex activated by silent visual stimuli that are sound-implying but that this activity also differentiates between sounds related to different categories such as animals, musical instruments and objects.

Antonio Damasio and his colleagues placed participants in an MRI scanner, while showing them silent, short videos which contained an implied sound ― for example, a dog barking or a musician playing a violin. When they analyzed the imaging data they found that activity from the auditory cortex recorded while subjects were seeing these videos was sufficient to classify whether the images being seen showed animals, musical instruments, or sound-producing objects.

The auditory cortex is usually thought to be activated only by sounds, and this study adds to evidence supporting the idea that sensory cortex activity is not driven entirely by sensory stimulation such as actually hearing a sound, but instead, also reflects perceptual experiences.